Thermal desorption of polychlorinated biphenyl and other volatile organic compounds from porous matrices such as soil or concrete can be achieved by various methods of heating the matrix by direct application of heat assisted by vacuum, gas purging, and the like. The method of applying heat, collection of the volatilized materials, e.g., polychlorinated biphenyl, and by-product production has a significant impact on the acceptability of any such method.
U.S. Pat. No. 5,253,597 discloses a high vacuum assisted volatilization method and apparatus for low heat removal of polychlorinated biphenyl from soils and sludge. Polychlorinated biphenyl compounds removal by incineration and pyrolysis under low vacuum are also known. The temperature at which such processes are conducted generally depends on the nature of the contaminated material and the volatility of the target contaminant as well as other components of the material.
Another thermal desorption process involves treatment of a heated slurry with a mixture of an alkaline material and a sulfoxide.
Countercurrent stripping with a vapor at temperatures below the boiling point of the contaminants is also used.